Battery diaphragm and preparation method thereof, battery and electric device

Abstract

The invention discloses a battery diaphragm and a preparation method thereof, a battery and a power utilization device, the battery diaphragm comprises a base membrane and a coating arranged on the base membrane, the base membrane comprises a pore structure, and part of the coating is also arranged in the pore structure; the coating includes a polymer electrolyte. The polymer electrolyte in the coating of the battery diaphragm has viscidity, the coating is arranged on the surface and in the pore structure of the base membrane, and the viscidity is beneficial to improving the binding force between the coating and the base membrane. In addition, the polymer electrolyte also has a soft contact characteristic, is beneficial to continuous and uniform distribution of the coating on the base membrane, can absorb the electrolyte, and is further in close contact with a pole piece by virtue of the viscosity of the polymer electrolyte, so that the wettability of the battery diaphragm to the electrolyte is favorably improved. In addition, the polymer electrolyte can also construct a continuous ion transmission channel in the battery diaphragm, so that the ion transmission resistance is reduced.

Description

Technical Field

[0001] The present application relates to the field of electrochemical energy storage, and in particular to a battery separator and a preparation method thereof, a battery, and an electrical device. Background Art

[0002] With the development of electrochemical energy storage technology, batteries (such as lithium-ion batteries) have been widely used in consumer electronics, electric vehicles, and energy storage. Market requirements for the performance, safety, and lifespan of secondary point batteries are also increasing. The performance of the battery separator, a key battery component, directly affects the overall performance and safety of the battery. Battery separators are typically made of materials such as polyethylene (PE) and polypropylene (PP). Traditional battery separators suffer from insufficient ion conductivity and interface properties. This can lead to poor electrolyte wettability and high interface impedance during use, affecting the battery's cycle performance and rate capability. Summary of the Invention

[0003] In view of this, the present application provides a battery separator and a preparation method thereof to solve at least one of the above-mentioned technical problems. In addition, the present application also provides a battery and an electrical device.

[0004] To achieve the above objectives, in a first aspect, the present application provides a battery separator, which includes a base membrane and a coating provided on the base membrane, the base membrane includes a pore structure, and part of the coating is provided in the pore structure; the coating includes a polymer electrolyte.

[0005] The polymer electrolyte in the battery separator coating of this application is viscous. The coating is located on the surface and in the pore structure of the base membrane, and this viscosity helps to improve the bonding strength between the coating and the base membrane. The polymer electrolyte also has soft contact properties, which helps to ensure the continuous and uniform distribution of the coating on the base membrane. It can also absorb electrolyte, and then rely on its viscosity to closely contact the electrode, thereby helping to improve the wettability of the battery separator to the electrolyte. In addition, the polymer electrolyte can also construct a continuous ion transmission channel in the battery separator, thereby reducing ion transmission resistance.

[0006] Based on the first aspect, in some possible implementations, the polymer electrolyte includes a first polymer and a lithium salt, and the first polymer includes one or more of polyethylene oxide, polyacrylate, polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene copolymer, polysiloxane, polyethylene glycol, sodium polystyrene sulfonate, polysulfone, polyethersulfone, polypropylene carbonate, polymethyl methacrylate, polyacrylonitrile and polyimide.

[0007] The mutual entanglement of polymer chains in the first polymer in the battery separator coating of the present application generates flow resistance, exhibiting viscosity, and the polymer chain structure of the first polymer can dissipate energy through chain segment rearrangement under external force, manifesting as soft contact and plastic deformation. The above-mentioned coating is arranged on the surface and pore structure of the base membrane. The viscosity of the first polymer helps to improve the bonding between the coating and the base membrane. At the same time, the soft contact (plastic deformation) characteristics of the first polymer help to continuously and evenly distribute the coating on the base membrane. It can also absorb electrolyte and then rely on its viscosity to closely contact the electrode, thereby helping to improve the wettability of the battery separator to the electrolyte. In addition, the lithium salt in the above-mentioned coating dissociates under the interaction of the polymer chain segments, which is conducive to the construction of continuous ion transmission channels in the battery separator, thereby reducing ion transmission resistance. Therefore, the electrolyte wettability and interfacial impedance of the battery using this battery separator are improved during the cycle process, which is conducive to improving the cycle performance and rate performance of the battery.

[0008] Based on the first aspect, in some possible implementations, the mass ratio of the first polymer to the lithium salt is 0.1 to 20.

[0009] Controlling the mass ratio of the first polymer and the lithium salt in the coating within the above range helps to simultaneously enhance the ionic conductivity of the battery separator and improve the interfacial properties of the battery separator.

[0010] Based on the first aspect, in some possible implementations, the mass ratio of the first polymer to the lithium salt is 0.1 to 5.

[0011] Controlling the mass ratio of the first polymer and the lithium salt in the coating within the above range helps to better enhance the ionic conductivity of the battery separator and improve the interface properties of the battery separator at the same time.

[0012] Based on the first aspect, in some possible implementations, the coating also includes a functional material, the functional material includes one or more of a second polymer, a plasticizer compound, an ionic liquid and an inorganic filler; the second polymer includes one or more of polyvinyl alcohol, polyacrylonitrile, polyethylene, polyamide, polydimethylsiloxane, polystyrene, polycaprolactone, polylactic acid and polymethyl ethylene carbonate, and the second polymer is different from the first polymer; the inorganic filler includes inorganic ceramic particles and an inorganic solid electrolyte.

[0013] When the coating of the present application also includes at least one of the above-mentioned functional materials, it helps to improve the chemical stability of the battery separator in the electrolyte, and can also synergistically improve the mechanical strength of the battery separator, thereby improving the puncture resistance of the battery separator, thereby improving the ability of the battery separator to resist lithium dendrite puncture and external pressure damage during the battery cycle. Secondly, it also helps to improve the thermal stability of the battery separator, thereby reducing the thermal shrinkage of the base film in a high temperature environment, thereby reducing the risk of short circuit of the positive and negative electrodes due to thermal shrinkage of the base film, reducing the occurrence of thermal runaway and improving the safety of the battery structure. In addition, the functional material can also synergize with the polymer electrolyte, such as reducing the crystallinity of the polymer, thereby improving the ionic conductivity of the battery separator, thereby further improving the interfacial impedance of the battery during the cycle and improving the rate performance of the battery.

[0014] Based on the first aspect, in some possible implementations, the mass ratio of the polymer electrolyte to the functional material is 0.1 to 10.

[0015] Controlling the mass ratio of polymer electrolyte to functional material in the coating within the above range helps to simultaneously enhance the ionic conductivity of the battery separator, improve the interfacial properties of the battery separator, and enhance the puncture resistance and thermal stability of the battery separator. Furthermore, it is beneficial to promote the synergistic effect of the functional material and the polymer electrolyte in improving the ionic conductivity of the battery separator.

[0016] Based on the first aspect, in some possible implementations, the base film has a thickness of 3 µm to 25 µm, and the coating has a thickness of 0.1 µm to 10 µm.

[0017] When the thickness of the base film and the coating is controlled within the above range, the battery separator has good ion conductivity and interface properties, as well as good mechanical strength, and the coating can maintain the integrity of the base film.

[0018] In the second aspect, the present application provides a method for preparing the above-mentioned battery separator, which comprises: mixing polymer electrolyte raw materials to form a coating material; coating the coating material on the surface of the base film to form a coating, and the coating method comprises one or more of roll coating, spray coating, gravure coating and micro-gravure coating.

[0019] The above coating method helps to improve the uniformity of the distribution of the coating material on the base film, thereby promoting the formation of a uniform coating on the base film. The uniform distribution of the coating is beneficial to improving the electrolyte wettability of the battery separator and reducing the interfacial impedance, thereby helping to improve the rate performance and cycle efficiency of the battery.

[0020] Based on the second aspect, in some possible implementations, the coating material further includes a leveling agent and a thickener. Based on the coating material, the content of the leveling agent is 0.001 wt% to 0.1 wt%, the content of the thickener is 0.1 wt% to 5 wt%, and the viscosity of the coating material is 50 mPa·s to 3000 mPa·s.

[0021] The above-mentioned additives help improve the uniformity and stability of the coating material and reduce the agglomeration or delamination of the coating material components. Controlling the amount of the leveling agent and thickener within the above-mentioned ranges helps further reduce the agglomeration or delamination of the coating material components. Controlling the viscosity of the coating material within the above-mentioned ranges helps further improve the uniformity and stability of the coating material.

[0022] In a third aspect, the present application provides a battery comprising a positive electrode plate, a negative electrode plate, an electrolyte and a separator, wherein the separator comprises the above-mentioned battery separator or the battery separator prepared by the above-mentioned preparation method.

[0023] The active ions (such as lithium ions) in the battery of the present application can be well conducted in the battery separator, and the electrolyte (electrolyte) can well infiltrate the separator interface, reducing the interfacial impedance, and the separator can remain stable in the electrolyte (electrolyte), and the thermal shrinkage of the separator is reduced, effectively avoiding battery failure caused by short circuit of the positive electrode. Therefore, the battery of the present application has higher rate performance, cycle efficiency and safety performance.

[0024] In a fourth aspect, the present application provides an electrical device comprising the above-mentioned battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the XRD spectrum of characteristic elements of the battery separator provided in Example 6 of the present application.

[0026] Figure 2 This is the EDS image of the characteristic element distribution of the battery separator provided in Example 6 of the present application, wherein Figure 2 (a) in the figure is a layered image. Figure 2 (b) in the figure is the distribution image of F elements. Figure 2 (c) in the figure is the distribution image of Cl element. Figure 2 (d) in the figure is the distribution image of Nb element.

[0027] Figure 3 This is an SEM image of a cross section along the thickness direction of the battery separator provided in Example 6 of the present application. DETAILED DESCRIPTION

[0028] The embodiments of the present application are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be understood as limiting the present application; it should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present application belongs; the embodiments of the present application and the features in the embodiments can be combined with each other unless there is a conflict; many specific details are set forth in the following description to facilitate a full understanding of the present application, and the embodiments described are only part of the embodiments of the present application, not all of the embodiments.

[0029] One embodiment of the present application provides a battery comprising a housing, an electrode assembly, and an electrolyte. The electrode assembly and the electrolyte are both located within the housing. In some embodiments, the battery comprises one or more of an all-solid-state battery, a semi-solid-state battery, and a liquid-state battery. In some embodiments, the battery comprises one or more of a lithium-ion battery, a sodium-ion battery, and a potassium-ion battery.

[0030] The outer shell can be a packaging bag obtained by packaging film (such as aluminum-plastic film), for example, a soft-pack battery. In other embodiments, it can also be a steel shell battery, an aluminum shell battery, etc.

[0031] The electrode assembly includes electrode sheets and separators. The electrode sheets include positive and negative electrodes. The separator is used to separate the positive and negative electrodes and can be provided between the positive and negative electrodes. In some embodiments, the electrode assembly can be a laminated structure, for example, it is formed by alternating layers of positive electrode sheets, separators, and negative electrode sheets. In other embodiments, the electrode assembly can also be a wound structure, for example, it is formed by stacking positive electrode sheets, separators, and negative electrode sheets in sequence and then winding them.

[0032] The active ions (such as lithium ions) in the battery of the present application can be well conducted in the battery separator, and the electrolyte (electrolyte) can well infiltrate the separator interface, reducing the interfacial impedance, and the separator can remain stable in the electrolyte (electrolyte), and the thermal shrinkage of the separator is reduced, effectively avoiding battery failure caused by short circuit of the positive electrode. Therefore, the battery of the present application has higher rate performance, cycle efficiency and safety performance.

[0033] diaphragm The separator comprises a battery separator, which comprises a base membrane and a coating layer arranged on the base membrane, wherein the base membrane comprises a pore structure, and a portion of the coating layer is arranged in the pore structure; the coating layer comprises a polymer electrolyte.

[0034] The polymer electrolyte in the battery separator coating of this application is viscous. The coating is located on the surface and in the pore structure of the base membrane, and this viscosity helps to improve the bonding strength between the coating and the base membrane. The polymer electrolyte also has soft contact properties, which helps to ensure the continuous and uniform distribution of the coating on the base membrane. It can also absorb electrolyte, and then rely on its viscosity to closely contact the electrode, thereby helping to improve the wettability of the battery separator to the electrolyte. In addition, the polymer electrolyte can also construct a continuous ion transmission channel in the battery separator, thereby reducing ion transmission resistance.

[0035] In some embodiments, the polymer electrolyte includes a first polymer and a lithium salt, and the first polymer includes one or more of polyethylene oxide, polyacrylate, polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene copolymer, polysiloxane, polyethylene glycol, sodium polystyrene sulfonate, polysulfone, polyethersulfone, polypropylene carbonate, polymethyl methacrylate, polyacrylonitrile and polyimide. The mutual entanglement of the polymer chains in the first polymer in the battery separator coating of the present application produces flow resistance, exhibits viscosity, and the polymer chain structure of the first polymer can dissipate energy by rearranging the chain segments under external force, which manifests as soft contact and plastic deformation. The above-mentioned coating is arranged on the surface and pore structure of the base film. The viscosity of the first polymer helps to improve the bonding force between the coating and the base film. At the same time, the soft contact (plastic deformation) characteristics of the first polymer help to continuously and evenly distribute the coating on the base film. It can also absorb the electrolyte, and then rely on its viscosity to closely contact the electrode, thereby helping to improve the wettability of the battery separator to the electrolyte. Furthermore, the lithium salt in the coating dissociates under the interaction of the polymer chain segments, which facilitates the construction of continuous ion transport channels in the battery separator, thereby reducing ion transport resistance. As a result, batteries using this battery separator have improved electrolyte wettability and interfacial impedance during cycling, thereby improving the battery's cycle performance and rate capability.

[0036] In some embodiments, scanning electron microscopy (SEM) can be used to observe that the coating layer fills the pore structure of the base film.

[0037] In some embodiments, the mass ratio of the first polymer to the lithium salt is 0.1 to 20. For example, the mass ratio of the first polymer to the lithium salt can be 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or any value within a range formed by any two of the foregoing values. Controlling the mass ratio of the first polymer to the lithium salt in the coating within the foregoing range helps to simultaneously enhance the ionic conductivity and improve the interfacial properties of the battery separator.

[0038] In some embodiments, the mass ratio of the first polymer to the lithium salt is 0.1 to 5. For example, the mass ratio of the first polymer to the lithium salt can be 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or any value within a range formed by any two of the foregoing values. Controlling the mass ratio of the first polymer to the lithium salt in the coating within the foregoing range helps to simultaneously enhance the ionic conductivity and improve the interfacial properties of the battery separator.

[0039] In some embodiments, the first polymer includes one or more of polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene copolymer, polyacrylonitrile, polyethylene oxide, and polyacrylate. The selection of the first polymer as above helps to improve the mechanical strength and ionic conductivity of the battery separator.

[0040] In some embodiments, the lithium salt includes one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium hexafluoroantimonate, lithium bis(trifluoromethanesulfonimide), lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium iodide, lithium magnesium bis(fluorosulfonyl)imide, lithium bisoxalatoborate, and lithium difluorooxalatoborate.

[0041] In some embodiments, the lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonimide), and lithium bis(fluorosulfonyl)imide. The lithium salt selected in the coating exhibits a large dipole moment and readily dissociates within the polymer, facilitating the formation of continuous ion transport channels within the battery separator, thereby reducing ion transport resistance. Furthermore, the lithium salt selected in the coating can react with the lithium metal anode to form a solid electrolyte interface (SEI) composed of a fluorine-containing inorganic compound.

[0042] In some embodiments, the material of the base film includes one or more of PP, PE, PP / PE composite, non-woven fabric, meta-aramid (PMIA), cellulose, polyvinylidene fluoride (PVDF), polyimide (PI), polyacrylonitrile (PAN) and polyethylene terephthalate (PET).

[0043] In some embodiments, the coating further comprises a functional material comprising one or more of a second polymer, a plasticizing compound, an ionic liquid, and an inorganic filler. The second polymer comprises one or more of polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyethylene (PE), polyamide (PA), polydimethylsiloxane (PDMS), polystyrene (PS), polycaprolactone (PCL), polylactic acid (PLA), and polymethyl ethylene carbonate (PPC), and the second polymer is different from the first polymer. The inorganic filler comprises inorganic ceramic particles and an inorganic solid electrolyte.

[0044] When the coating of the present application also includes at least one of the above-mentioned functional materials, it helps to improve the chemical stability of the battery separator in the electrolyte, and can also synergistically improve the mechanical strength of the battery separator, thereby improving the puncture resistance of the battery separator, thereby improving the ability of the battery separator to resist lithium dendrite puncture and external pressure damage during the battery cycle. Secondly, it also helps to improve the thermal stability of the battery separator, thereby reducing the thermal shrinkage of the base film in a high temperature environment, thereby reducing the risk of short circuit of the positive and negative electrodes due to thermal shrinkage of the base film, reducing the occurrence of thermal runaway and improving the safety of the battery structure. In addition, the functional material can also synergize with the polymer electrolyte, such as reducing the crystallinity of the polymer, thereby improving the ionic conductivity of the battery separator, thereby further improving the interfacial impedance of the battery during the cycle and improving the rate performance of the battery.

[0045] In some embodiments, the functional material includes inorganic ceramic particles. Inorganic ceramic particles have good thermal stability and help improve the thermal stability of the battery separator.

[0046] In some embodiments, the functional material includes inorganic ceramic particles and a second polymer. The inorganic ceramic particles and the second polymer work together to help improve the puncture resistance of the battery separator.

[0047] In some embodiments, the functional material includes an inorganic solid electrolyte, which can synergistically improve the ionic conductivity of the battery separator with the polymer electrolyte.

[0048] In some embodiments, the mass ratio of the polymer electrolyte to the functional material is 0.1 to 10. For example, the mass ratio of the polymer electrolyte to the functional material can be 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 or any value within the range formed by any two of the above values. Controlling the mass ratio of the polymer electrolyte to the functional material in the coating within the above range helps to simultaneously improve the ionic conductivity of the battery separator, improve the interfacial properties of the battery separator, and improve the puncture resistance and thermal stability of the battery separator. In addition, it is also beneficial to promote the synergistic effect of the functional material and the polymer electrolyte in improving the ionic conductivity of the battery separator.

[0049] In some embodiments, the second polymer includes one or more of polystyrene (PS), polycaprolactone (PCL), polylactic acid (PLA), and poly(methyl ethylene carbonate) (PPC). Selecting the above second polymers can help reduce the crystallinity of the polymer, improve the ionic conductivity of the battery separator, and enhance the mechanical strength of the battery separator.

[0050] In some embodiments, the plasticizing compound includes one or more of succinonitrile (SN), ethylenediaminetetraacetic acid (EDTA), dioctyl phthalate (DOP), diisononyl phthalate (DINP), diisooctyl phthalate (DIDP), diethylhexyl phthalate (DEHP), divinyl ether (DEG), trivinyl ether (TEG), polyethylene glycol (PEG), polypropylene glycol (PPG), glycerin, propylene glycol, and polydimethylsiloxane (PDMS). These plasticizing compounds are selected to synergistically improve the ionic conductivity of the battery separator by reducing the crystallinity of the polymer.

[0051] In some embodiments, the ionic liquid includes one or more of an imidazolium ionic liquid, a pyridine ionic liquid, a quaternary ammonium ionic liquid, a quaternary phosphonium ionic liquid, a pyrrolidine ionic liquid, and a piperidine ionic liquid. In some embodiments, the cation of the imidazolium ionic liquid includes: 1-alkyl imidazole, 1-alkane-3-methyl imidazole, or 1-alkyl-2,3-dimethyl imidazole, wherein the alkyl group can be methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, or octadecyl; the anion of the imidazolium ionic liquid includes: chloride, bromine, iodine, tetrafluoroboric acid, hexafluorophosphoric acid, acetic acid, bis(trifluoromethanesulfonyl)imide, nitric acid, perchloric acid , hydrogen sulfate, dihydrogen phosphate, trifluoromethanesulfonic acid, trifluoroacetic acid, or p-toluenesulfonic acid; for example, the imidazolium ionic liquid is selected from one or more of 1-methylimidazolium chloride, 1-methylimidazolium tetrafluoroborate, N-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-octyl-3-methylimidazolium hexafluorophosphate. In some embodiments, the cation of the pyridinium ionic liquid includes N-alkylpyridine, wherein the alkyl group can be ethyl, butyl, hexyl, or octyl; the anion of the pyridinium ionic liquid includes chloride, bromine, tetrafluoroborate, hexafluorophosphate, or bis(trifluoromethanesulfonyl)imide; for example, the pyridinium ionic liquid is selected from one or more of N-ethylpyridinium chloride, N-ethylpyridinium tetrafluoroborate, and N-ethylpyridinium bis(trifluoromethanesulfonyl)imide. In some embodiments, the cation of the quaternary ammonium ionic liquid includes: tetraethylammonium, tetrabutylammonium, alkyltriethylammonium or alkyltributylammonium, wherein the alkyl group can be ethyl, butyl, hexyl or octyl; the anion of the quaternary ammonium ionic liquid includes: chloride, bromine, tetrafluoroboric acid, hexafluorophosphoric acid or bistrifluoromethanesulfonimide; for example, the quaternary ammonium ionic liquid is selected from one or more of trimethylamine hydrochloride, N,N-diethylmethylammonium trifluoromethanesulfonate and triethylammonium hydrochloride. In some embodiments, the cation of the quaternary phosphonium ionic liquid includes: alkyl tributyl phosphonium, wherein the alkyl group can be ethyl, butyl, hexyl, or octyl; the anion of the quaternary phosphonium ionic liquid includes: bromine, tetrafluoroboric acid, and bis(trifluoromethanesulfonyl)imide; for example, the quaternary phosphonium ionic liquid is selected from one or more of methyl tributyl phosphonium bis(trifluoromethanesulfonyl)imide, ethyl tributyl phosphonium bis(trifluoromethanesulfonyl)imide, propyl tributyl phosphonium bis(trifluoromethanesulfonyl)imide, N-n-hexyl quaternary ammonium bis(trifluoromethanesulfonyl)imide, N-trimethyl-N-pentyl quaternary ammonium trifluoromethanesulfonylimide, and N-trimethyl-N-butyl quaternary ammonium trifluoromethanesulfonylimide.In some embodiments, the cation of the pyrrolidine ionic liquid includes: N-alkyl-N-methylpyrrolidine, wherein the alkyl group can be ethyl, propyl, butyl, hexyl, or octyl; the anion of the pyrrolidine ionic liquid includes: bromine, tetrafluoroboric acid, hexafluorophosphoric acid, and bis(trifluoromethanesulfonyl)imide; for example, the pyrrolidine ionic liquid is selected from one or more of N-ethyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide, N-propyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide, and N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide. In some embodiments, the cations of piperidine-based ionic liquids include N-alkyl-N-methylpiperidines, where the alkyl group can be ethyl, propyl, butyl, hexyl, or octyl. Anions include bromine, tetrafluoroboric acid, hexafluorophosphoric acid, and bis(trifluoromethanesulfonyl)imide. For example, the piperidine-based ionic liquid is selected from one or more of N-ethyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide, N-propyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide, and N-butyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide. These ionic liquids synergistically improve the ionic conductivity of the battery separator by reducing the crystallinity of the polymer.

[0052] In some embodiments, the inorganic ceramic particles may include one or more of hafnium dioxide, strontium titanate, tin dioxide, cesium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium oxide, yttrium oxide, aluminum oxide, titanium oxide, silicon dioxide, boehmite, magnesium hydroxide, or aluminum hydroxide.

[0053] In some embodiments, the inorganic solid electrolyte comprises one or more of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte. In some embodiments, the oxide solid electrolyte is selected from one or more of a NASICON structure material, a perovskite structure material, an antiperovskite structure material, a LISICON structure, and a garnet structure material. In some embodiments, the sulfide solid electrolyte is selected from a sulfide such as Li2S-P2S5, Li 10 GeP2S 12 , Li3PS4 and Li 6- x PS 5-x Cl 1+x One or more of, wherein 0≤x≤0.8. In some embodiments, the general formula of the halide solid electrolyte material is: Li a (M b )X c X' d, wherein 0.5≤a≤5, 0.2≤b≤4, c+d=a+bε, wherein ε is the weighted average valence of the M element, Li is a lithium ion, M includes one or more of Ga, Y, In, Mg, Sr, Sc, Sn, Pb, Ti, Zr, Hf, Nb, Ta, W, Fe, Ru, Al and lanthanide metal elements, X includes one or more of the halogen elements, X' includes one or more of the halide ion, N ion, oxygen-containing anion group and pseudohalide anion, wherein the oxygen-containing anion group includes O 2- 、S 2- 、CN - 、CO3 2- PO4 3- 、P2O7 4- and SO4 2- One or more of the pseudohalide anions include SCN - PF6 - NH2 - 、AlF4 - and BF4 - One or more of .

[0054] In some embodiments, the inorganic solid electrolyte includes Li 3x La 2 / 3-x TiO(LLTO, 0≤x≤0.16), Li 1+ x Al x Ti 2-x (PO4)3(LATP), Li 1+x Al x Ge 2-x (PO4)3(LAGP), Li7La3Zr2O 12 (LLZO), Li2S-P2S5, Li6PS5Cl1, Li2MnCl4, Li2ZnCl4, Li2ZrOCl4, LiYbF4, LiAlF4, Li3YCl6, Li3InCl6, Li3InCl 5.5 F 0.5 、Li3TaCl6、LiNbOCl4、Li 0.388 Ta 0.238 La 0.475 One or more of Cl3 and Li6CoCl8. The inorganic solid electrolyte selected from the above substances has an ion-conducting effect, and can also improve ion conductivity by reducing the crystallinity of the polymer in the coating.

[0055] In some embodiments, the thickness of the base film is 3 µm to 25 µm, and the thickness of the coating is 0.1 µm to 10 µm. For example, the thickness of the base film can be 3 µm, 5 µm, 7 µm, 9 µm, 11 µm, 13 µm, 15 µm, 17 µm, 19 µm, 21 µm, 23 µm, 25 µm, or any value within the range formed by any two of the above values. The thickness of the coating can be 0.1 µm, 0.5 µm, 1 µm, 2 µm, 3 µm, 4 µm, 5 µm, 6 µm, 7 µm, 8 µm, 9 µm, 10 µm, or any value within the range formed by any two of the above values. When the thickness of the base film and the coating is controlled within the above range, the battery separator has good ion conductivity and interface properties, as well as good mechanical strength, and the coating can maintain the integrity of the base film.

[0056] In some embodiments, the battery separator includes at least one coating layer. It is understood that the battery separator of the present application may include multiple coating layers. When coating layers are provided on two opposing surfaces of the base film, multiple coating layers may be provided on top of the existing coating layers. Providing multiple coating layers on the base film surface helps to better maintain the integrity of the battery separator.

[0057] Positive electrode The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector. The positive electrode active material layer includes a positive electrode material, a binder and a conductive material.

[0058] In some embodiments, the positive electrode current collector may be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as but not limited to a current collector formed by combining the aforementioned conductive foil and a polymer substrate.

[0059] In some embodiments, the positive electrode material includes a compound that reversibly intercalates and deintercalates lithium ions (i.e., a lithiated intercalation compound). In some embodiments, the positive electrode material may include a lithium transition metal composite oxide. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel. In some embodiments, the positive electrode material may include, but is not limited to, lithium manganese iron phosphate (LiFe x Mn y PO4, x+y=1), at least one of lithium iron phosphate, lithium manganate, lithium cobaltate, lithium nickelate, lithium-rich manganese-based, lithium nickel manganate (LMNO) or lithium vanadium oxyphosphate (LiVOPO4).

[0060] In some embodiments, the binder may include but is not limited to at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin or nylon.

[0061] In some embodiments, the conductive material includes, but is not limited to, a carbon-based material, a metal-based material, a conductive polymer, or any combination thereof. In some embodiments, the carbon-based material may include, but is not limited to, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material may include, but is not limited to, metal powder or metal fiber, such as copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative.

[0062] Negative electrode The negative electrode sheet may be only a negative electrode current collector. The negative electrode sheet may also include a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode material, a binder and a conductive material.

[0063] In some embodiments, the negative electrode current collector may use at least one of copper foil, nickel foil, stainless steel foil, titanium foil or a carbon-based current collector, or may be any composite current collector disclosed in the prior art, such as but not limited to a current collector formed by combining the aforementioned conductive foil and a polymer substrate, wherein the polymer substrate includes one or more of polyethylene, polyethylene terephthalate, polyimide, polypropylene, polyethylene, polyamide and polyphenylene sulfide, with a thickness of 1 μm to 300 μm, and the thickness of the conductive foil is 0.1 μm to 100 μm.

[0064] In some embodiments, the negative electrode material includes graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiOx (0.5<x<1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structured lithium titanate, lithiated TiO2-Li4Ti5O 12 , Li-Al alloy and at least one of metallic lithium.

[0065] In some embodiments, the binder may include but is not limited to polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin or nylon, etc.

[0066] In some embodiments, the conductive material includes, but is not limited to, a carbon-based material, a metal-based material, a conductive polymer, or any combination thereof. In some embodiments, the carbon-based material may include, but is not limited to, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material may include, but is not limited to, metal powder or metal fiber, such as copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative.

[0067] electrolytes The electrolyte conducts ions between the positive and negative electrodes. The electrolyte can be in one or more of a gel, solid, and liquid state. In some embodiments, the electrolyte is an electrolyte solution.

[0068] In some embodiments, the electrolyte includes a lithium salt and an organic solvent. In some embodiments, the total concentration of the lithium salt in the electrolyte is 0.5 mol / L to 5 mol / L. In some embodiments, the lithium salt includes one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium hexafluoroantimonate, lithium bis(trifluoromethanesulfonimide), lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium iodide, lithium magnesium bis(fluorosulfonyl)imide, lithium bisoxalatoborate, and lithium difluorooxalatoborate. In some embodiments, the organic solvent includes one or more of an ester organic solvent, an ether organic solvent, and an ionic liquid. In some embodiments, the ester organic solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, dimethyl sulfite, diethyl sulfite, dipropyl sulfite, ethylene sulfite, methyl acetate, ethyl acetate, ethyl formate, ethyl propionate, and methyl propionate. In some embodiments, the ether organic solvent includes one or more of ethylene glycol n-butyl ether, methyl butyl ether, methyl tert-butyl ether, dibutyl ether, ethylene glycol dimethyl ether, 1,3-dioxolane, tetraethylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, diethylene glycol dimethyl ether and triethylene glycol dimethyl ether.

[0069] In some embodiments, the electrolyte further comprises an organic additive. For example, the additive comprises one or more of tripropynyl phosphate, 4-nitrophenyl trifluoroacetate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,3-propane sultone, vinyl sulfate, toluene, 1,2-xylene, 1,3-xylene, 1,4-xylene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, and hexafluorobenzene. In some embodiments, the volume ratio of the organic additive to the organic solvent is 0.1 to 10.

[0070] In some embodiments, the electrolyte further comprises an inorganic additive. For example, the inorganic additive comprises one or more of vinylene carbonate, fluoroethylene carbonate, and LiNO 3 . In some embodiments, the inorganic additive comprises 0.1 wt % to 10 wt % of the electrolyte.

[0071] One embodiment of the present application further provides an electrical device comprising the above-mentioned battery. In some embodiments, the battery of the present application can be used in, but is not limited to, the following electrical devices: laptop computers, pen-type computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries or lithium-ion capacitors, etc.

[0072] Another embodiment of the present application provides a method for preparing a battery separator, the method comprising: Step 1: Mix polymer electrolyte raw materials to form a coating material.

[0073] Step 2: coating the coating material on the surface of the base film to form a coating layer, and the coating method includes one or more of roller coating, spray coating, gravure coating and micro gravure coating.

[0074] The above coating method helps to improve the uniformity of the distribution of the coating material on the base film, thereby promoting the formation of a uniform coating on the base film. The uniform distribution of the coating is beneficial to improving the electrolyte wettability of the battery separator and reducing the interfacial impedance, thereby helping to improve the rate performance and cycle efficiency of the battery.

[0075] In some embodiments, the coating material further includes a leveling agent and a thickener, and based on the coating material, the amount of the leveling agent is 0.001wt% to 0.1wt%, and the amount of the thickener is 0.1wt% to 5wt%. For example, the amount of the leveling agent can be 0.001wt%, 0.005wt%, 0.010wt%, 0.020wt%, 0.030wt%, 0.040wt%, 0.050wt%, 0.060wt%, 0.070wt%, 0.080wt%, 0.090wt%, 0.1wt% or any value within the range of any two of the above numerical values. The amount of the thickener can be 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% or any value within the range of any two of the above numerical values. The above additives help to improve the uniformity and stability of the coating material and reduce the agglomeration or stratification of the coating material components. Controlling the amount of the leveling agent and the thickener within the above range helps to better reduce the agglomeration or delamination of the coating material components.

[0076] In some embodiments, the viscosity of the coating material is between 50 mPa·s and 3000 mPa·s. For example, the viscosity of the coating material can be 50 mPa·s, 100 mPa·s, 300 mPa·s, 500 mPa·s, 800 mPa·s, 1000 mPa·s, 1300 mPa·s, 1500 mPa·s, 1800 mPa·s, 2000 mPa·s, 2300 mPa·s, 2500 mPa·s, 2800 mPa·s, 3000 mPa·s, or any value within a range formed by any two of the foregoing values. Controlling the viscosity of the coating material within the foregoing range helps to improve the uniformity and stability of the coating material.

[0077] In some embodiments, the leveling agent includes one or more of acrylic resin, urea-formaldehyde resin, melamine-formaldehyde resin, CAB, and polyvinyl butyral.

[0078] In some embodiments, the thickener includes one or more of carboxymethyl cellulose (CMC), sodium alginate (SA), terpineol, polyacrylic acid (PAA), polyvinyl alcohol (PVA), xanthan gum, gum arabic (AG), gelatin, and guar gum (GA).

[0079] In some embodiments, the solvent includes one or more of acetonitrile, acetone, ethyl acetate, butanone, diethyl ether, hexane, n-heptane, chloroform, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, 2,2,2-trifluoro-N,N-dimethylformamide, and N-methylpyrrolidone.

[0080] The present invention will be explained below in conjunction with the embodiments. It will be understood by those skilled in the art that the following examples are only used to explain the present invention and are not to be construed as limiting the present invention. Unless otherwise indicated, the reagents, software, and instruments not specifically described in the following examples are all conventional commercially available products or open source.

[0081] Example 1: (1) A battery separator, the preparation method of which comprises: Step 1: PVDF, lithium bis(trifluoromethanesulfonimide) and N,N-dimethylformamide are added to a stirred tank with a mass ratio of PVDF to lithium salt of 10:7. Acrylic resin is added as a leveling agent and carboxymethyl cellulose as a thickener, and the mixture is stirred evenly. A non-oxygen inert gas is introduced to discharge oxygen from the stirred tank and the materials, and a certain pressure is maintained. Circulating water is passed to keep the temperature in the stirred tank below 50°C. The mixture is stirred for 2 hours to form an initial slurry, which is then cooled to 35°C to 45°C. The mixture is demagnetized using a demagnetization pump and then sand-milled using a sand mill to grind the inorganic electrolyte in the initial slurry to a target particle size of 300 nm to obtain a coating material having a viscosity of 50-100 mPa·s. Step 2: Apply the coating material to one side of the PE (porous base membrane) by roller coating, bake it in an oven at 55°C to remove the solvent, and then roll it up to obtain a battery separator.

[0082] (2) A battery, the preparation method of which comprises: assembling an electrode assembly using lithium nickel cobalt manganese oxide as a positive electrode sheet, lithium metal as a negative electrode sheet, and the battery separator obtained in (1), injecting an ether electrolyte, and obtaining a battery.

[0083] Example 2: The difference from Example 1 is that in (1), the raw materials for the first step are PVDF, lithium bis(trifluoromethanesulfonimide), and polyethylene oxide.

[0084] Example 3: The difference from Example 1 is that in (1), the raw materials for the first step are PVDF, lithium bis(trifluoromethanesulfonimide) and succinonitrile.

[0085] Example 4: The difference from Example 1 is that in (1), the raw materials for the first step are PVDF, lithium bis(trifluoromethanesulfonyl)imide, and N-ethylpyridine bis(trifluoromethanesulfonyl)imide salt.

[0086] Example 5: The difference from Example 1 is that in (1), the raw materials for the first step are PVDF, lithium bis(trifluoromethanesulfonimide), Al2O3, and SiO2.

[0087] Example 6: The difference from Example 1 is that in (1), the raw materials for the first step are PVDF, lithium bis(trifluoromethanesulfonimide) and LNOC.

[0088] Example 7: The difference from Example 1 is that in (1), the raw materials for the first step are PVDF, lithium bis(trifluoromethanesulfonimide), polymethyl methacrylate, Al2O3, and SiO2.

[0089] Example 8: The difference from Example 1 is that in (1), the mass ratio of PVDF to lithium bis(trifluoromethanesulfonimide) is 1:1.

[0090] Comparative Example 1: The PE (base film) of Example 1 was used as a battery separator.

[0091] Comparative Example 2: The difference from Example 1 is that in (1), the raw materials for the first step are PTFE, lithium bis(trifluoromethanesulfonimide), polyethylene oxide, Al2O3, and SiO2.

[0092] The test methods for battery separators and batteries in this application are as follows: 1. Base film material test: The base film material can be characterized by differential scanning calorimetry (DSC). The characteristic peak of PE is at 120-130℃, the characteristic peak of PP is at 160-170℃, the characteristic peak of meta-aramid is at 300-400℃, the characteristic peak of cellulose is at 220-240℃, the characteristic peak of polyvinylidene fluoride is at 160-170℃, the characteristic peak of polyimide is at 200-300℃, the characteristic peak of polyacrylonitrile is at 180-200℃, and the characteristic peak of polyethylene terephthalate is at 220-240℃. If the DSC characteristic peak positions of the base film materials overlap, infrared testing is required to determine the membrane material. The infrared characteristic peak position of PE is 2800-3000cm -1 , 1500-1350cm -1 , 750-700cm -1 and 1200-950cm -1 The infrared characteristic peak of PP is 2800-3000cm -1 , 1500-1350cm -1 and 1200-950cm -1 The infrared characteristic peak position of cellulose is 3100-3000cm -1 , 2900-2700cm -1 , 1100-1000cm -1 , and 900-800cm -1 The infrared characteristic peak position of meta-aramid is 1700-1500cm -1 , 1600-1500cm -1 and 1300-1200cm -1 The infrared characteristic peak of polyvinylidene fluoride is 3000-2900cm -1 , 1500-1300cm-1 , 900-800cm -1 , 600-400cm -1 The infrared characteristic peak of polyimide is 3600-3000cm -1 , 1800-1700cm -1 , 1600-1500cm -1 , 1300-1200cm -1 and 700-900cm -1 The infrared characteristic peak of polyacrylonitrile is 2300-2200cm -1 and 1800-1700cm -1 The infrared characteristic peak of polyethylene terephthalate is 3600-3300cm -1 , 1800-1700cm -1 , 1300-1200cm -1 and 1300-1100cm -1 .

[0093] 2. Micromorphology test of battery separator: Scanning electron microscope (SEM) can be used to characterize the micromorphology of battery separator. The structure can be single-layer or multi-layer. If it is a multi-layer structure, the material of each layer is not specified.

[0094] 3. Battery separator thickness test: can be tested with a thickness tester.

[0095] 4. Characteristic element test of coating: X-ray photoelectron spectroscopy (XPS) can be used to characterize the characteristic elements of battery separator coating, among which characteristic peaks can appear in the ranges of 54-56eV (lithium), 71-73eV (aluminum), 130-140eV (phosphorus), 161-164eV (sulfur), 175-180eV (zirconium), 197-200eV (chlorine), 283-286eV (carbon), 346-348eV (calcium), 457-459eV (titanium), 463-465eV (titanium), 640-642eV (manganese), 680-691eV (fluorine), 775-785eV (barium), 1020-1025eV (zinc) and 1302-1304eV (magnesium).

[0096] 5. Characteristic element distribution test of the coating: The selected area is grid scanned by an energy dispersive spectrometer (EDS), and the X-ray signal of each pixel is recorded to generate a two-dimensional distribution map of each element to characterize the characteristic elements.

[0097] 6. Polymer testing: Infrared testing can be used to characterize the polymer in the battery separator coating. The main characteristic peak of polyethylene oxide is 1100 cm -1 (COC symmetrical telescopic), 960cm -1 and 840cm -1 The combined peak, 2875cm -1 (CH stretching); main characteristic peaks of polyvinylidene fluoride: 1400-1100cm -1 (CF stretching vibration), 840-880cm -1 (CH vibration); polyvinylidene fluoride hexafluoropropylene copolymer contains HFP copolymer units, and its CF stretching peak (~1175cm -1 ) is shifted compared to PVDF; the main characteristic peak of polyacrylonitrile is 2240-2250cm -1 (C≡N stretching vibration peak), 2940-2980cm -1 (CH stretching vibration) and 1450cm -1 (CH bending vibration), 800-830 cm -1 (CH swing peak).

[0098] 7. Inorganic solid electrolyte test: The inorganic solid electrolyte is identified by X-ray diffraction (XRD), LLTO (Li 3x La 2 / 3-x TiO3): has a perovskite structure with characteristic peaks at 23.8°, 32.5°, 48.7° (2θ); LATP (Li 1+x Al x Ti 2-x (PO4)3): has NASICON structure, with characteristic peaks at 21.2°, 23.9°, 27.6° (2θ); LAGP (Li 1+x Al x Ge 2-x (PO4)3): Similar to LATP; LLZO (Li7La3Zr2O 12 ): characteristic peaks of cubic phase at 29.7°, 34.3°, 43.6° (2θ); Li2S-P2S5: characteristic peaks at 27.5°, 30.1°, 32.8° (2θ); Li6PS5Cl: main peaks at 25.3°, 29.8° (2θ); LiNbOCl4 (LNOC): characteristic peaks at 30.2°, 34.8°, 38.9° (2θ).

[0099] 8. Testing of solvents in coating materials: Solvents were identified by gas chromatography-mass spectrometry (GC-MS). Acetone: molecular ion peak 58 (C3H6O); ethyl acetate: molecular ion peak 88 (C4H8O2), characteristic fragments m / z=43,61; butyl butyrate: molecular ion peak 116 (C6H 12 O2), characteristic fragments m / z=56,73; DMF: molecular ion peak 73 (C3H7NO), characteristic fragments m / z=42,44,58.

[0100] 9. Battery separator ion conductivity test: Use two pieces of stainless steel to clamp the battery separator, place it in a 2032 battery shell, and use an electrochemical AC impedance spectrometer to measure. The ionic conductivity is calculated using the formula: σ = L / AR, where L is the thickness of the battery separator, A is the area of ​​the stainless steel sheet at room temperature, and R is the measured impedance.

[0101] 10. Battery Separator Mechanical Properties Test: Cut multiple rectangular specimens of consistent specifications from the battery separator, ensuring that the edges are flat and free of cracks. Specimen dimensions are cut according to ASTM D882. The specimens are placed in a standard laboratory environment (temperature 23°C ± 2°C, relative humidity 50% ± 5%) and allowed to equilibrate for at least 24 hours to minimize environmental impact on membrane performance. Secure the battery separator specimens to the fixture of the tensile tester, ensuring that their edges are aligned and wrinkle-free. Set the tensile speed, start the tensile tester, and record the force-displacement data during the stretching process. When the specimen breaks, record the force and elongation at the breaking point.

[0102] 11. Thermal Shrinkage Test for Battery Separators: The thermal shrinkage test method for battery separators refers to GB / T 36363-2018. Take a 100 mm x 100 mm battery separator sample and mark the machine direction (MD) and transverse direction (TD) dimensions. Perform at least three sets of tests to ensure test repeatability. Test temperature: 105°C, test time: 30 minutes. Measure the initial dimensions of the specimen in the machine direction (MD) and transverse direction (TD) using a measuring tool with an accuracy of 0.01 mm. Place the sample in a hot air circulating oven (without strong convection) for 30 minutes. Remove the sample, cool it at ambient conditions for 10 minutes, and measure the longitudinal and transverse dimensions after heating.

[0103] 12. Battery separator peel strength test: Refer to GB / T 36363-2018, "Technical Specifications for Lithium-ion Battery Separators." Take a 15 mm x 200 mm separator sample. Perform at least five tests to ensure repeatability. Use a blade or tape to partially peel the coating and base film approximately 30 mm apart, forming the section to be stretched. Clamp the base film to the fixed end of an electronic tensile testing machine, and the coating to the moving end. Peel angle: 180°, peel speed: 100 mm / min. Record the peel force (N) during the test and plot the peel curve.

[0104] 13. Battery Rate Performance Test: The rate performance test is conducted at 25±2°C. The battery cell is charged to 4.3 V using a 0.2 C constant current-constant voltage (CC-CV) mode with a cutoff current of 0.05 C. It is then discharged to 3.0 V at rates of 0.2 C, 0.5 C, and 1 C. Between each rate, the cell is fully charged at 0.2 C and allowed to rest for 10 minutes before the next rate test. Based on the 0.2 C discharge capacity, the capacity retention rate at a 1 C rate is calculated as the rate performance evaluation metric.

[0105] 14. Battery Cycling Performance Test: Cycling performance testing is conducted at 25±2°C. The battery cell is charged to 4.3 V using a 0.3 C constant current-constant voltage (CC-CV) method with a cutoff current of 0.05 C. It is then discharged to 3.0 V at a constant current of 1 C to complete one cycle. During the cycling process, the discharge capacity is recorded at every specified cycle (e.g., every 50 or 100 cycles) and compared with the initial capacity to assess capacity retention and cycle life. Testing can continue until the capacity decays to 80% of the initial capacity or the set number of cycles is reached.

[0106] Taking Example 6 of the present application as an example, the characteristic elements of the battery separator were analyzed by XRD. Figure 1 The characteristic peak at the “*” matches the characteristic peak range of LiNbOCl4 (LNOC), indicating that the battery separator has the characteristic peak of LNOC. The above results show that the battery separator provided by the embodiment of the present application can contain an inorganic solid electrolyte.

[0107] Taking Example 6 of the present application as an example, the characteristic element distribution analysis of the battery separator was performed by SEM and EDS. Figure 2 , Figure 2 (a) shows the EDS image of the battery separator. Figure 2 (b) shows the distribution of F elements, and the results show that the lithium salt is evenly distributed in the battery separator coating. Figure 2 (c) and Figure 2 (d) shows the distribution of Cl and Nb elements, respectively, indicating a uniform distribution of LNOC in the battery separator coating. These results demonstrate that the preparation process of this embodiment can produce a coating with uniform component distribution, and the coating is also evenly distributed on the base film.

[0108] Taking Example 6 of the present application as an example, the morphology of the battery separator was analyzed by SEM. Figure 3The results show that the polymer electrolyte coating is distributed on the surface of the porous base membrane, and part of the coating fully penetrates the pores of the porous base membrane. These results show that the battery separator of the present embodiment includes the first polymer, whose viscosity and soft contact properties help the coating to be continuously distributed on the surface and in the pore structure of the porous base membrane, forming good contact, and in combination with the lithium salt, it is conducive to the construction of continuous ion transmission channels.

[0109] The battery separators of Examples 1-8 and Comparative Examples 1-2 were tested for ionic conductivity, mechanical strength, thermal shrinkage, and peel strength. The results are shown in Table 1. The batteries of Examples 1-8 and Comparative Examples 1-2 were also tested for rate performance and cycle performance. The results are shown in Table 2.

[0110] Table 1. Battery separator performance test of Examples 1-8 and Comparative Examples 1-2 of the present application Table 2. Battery performance test of Examples 1-8 and Comparative Examples 1-2 of the present application The coating of the battery separator of Examples 1-8 of the present application includes a polymer electrolyte (including a first polymer and a lithium salt), wherein the mutual entanglement of the polymer chains in the first polymer generates flow resistance and exhibits viscosity. At the same time, the polymer chain structure of the first polymer can dissipate energy through chain segment rearrangement under external force, exhibiting soft contact and plastic deformation. Therefore, the above-mentioned coating is arranged on the surface and pore structure of the base membrane. The viscosity of the first polymer helps to improve the bonding force between the coating and the base membrane. At the same time, the soft contact (plastic deformation) characteristics of the first polymer help to continuously and evenly distribute the coating on the base membrane, thereby helping to improve the wettability of the battery separator to the electrolyte. In addition, the lithium salt in the above-mentioned coating dissociates under the interaction of the polymer chain segments, which is conducive to the construction of a continuous ion transmission channel in the battery separator, thereby reducing the ion transmission resistance.

[0111] Among them, the battery separators of Examples 2-7 further include functional materials, which help to improve the chemical stability of the battery separator in the electrolyte, and can also synergistically improve the tensile strength of the battery separator, thereby improving the mechanical strength and puncture resistance of the battery separator, thereby improving the ability of the battery separator to resist lithium dendrite puncture and external pressure damage during battery operation. Secondly, it also helps to improve the thermal stability of the battery separator, thereby reducing the thermal shrinkage of the base film in a high temperature environment, maintaining the integrity of the separator, delaying the occurrence of thermal runaway, and helping to improve the stability of the battery structure. In addition, the functional materials can also cooperate with the polymer electrolyte, such as reducing the crystallinity of the polymer, thereby improving the ionic conductivity of the battery separator, thereby further improving the interfacial impedance of the battery during the cycle and improving the rate performance of the battery.

[0112] Among them, in the battery separator of Example 8, the mass ratio of the first polymer and the lithium salt further satisfies the preset relationship (0.1-5), which can more significantly improve the ionic conductivity of the battery separator and improve the interface performance of the battery separator at the same time.

[0113] Compared with Examples 1-8, Comparative Example 1 uses a base film as a battery separator, which is prone to thermal shrinkage or melting under high temperature conditions, resulting in battery short circuit, thus posing a serious safety hazard. In addition, there are also problems such as poor puncture resistance, poor electrolyte wettability, and high interface impedance, which affect the battery's cycle performance and rate performance.

[0114] Compared with Examples 1-8, Comparative Example 2 uses a base film with different coatings as a battery separator. The material in its coating does not have the viscosity and soft contact properties of the polymer electrolyte of the present application, and the lithium salt in the coating has poor dissociation ability in the absence of the first polymer. The ionic conductivity of the resulting battery separator is not as good as that of the examples of the present application.

[0115] The above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present application should not depart from the spirit and scope of the technical solutions of the present application.

Claims

1. A battery separator, characterized in that: The battery separator includes a base film and a coating layer provided on the base film, wherein the base film includes a pore structure, and a portion of the coating layer is provided in the pore structure; The coating includes a polymer electrolyte.

2. The battery separator according to claim 1, wherein The polymer electrolyte includes a first polymer and a lithium salt, wherein the first polymer includes one or more of polyethylene oxide, polyacrylate, polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene copolymer, polysiloxane, polyethylene glycol, sodium polystyrene sulfonate, polysulfone, polyethersulfone, polypropylene carbonate, polymethyl methacrylate, polyacrylonitrile and polyimide.

3. The battery separator according to claim 2, wherein The mass ratio of the first polymer to the lithium salt satisfies at least one of the following conditions: (1) The mass ratio of the first polymer to the lithium salt is 0.1 to 20; (2) The mass ratio of the first polymer to the lithium salt is 0.1 to 5.

4. The battery separator according to claim 1, wherein The coating further comprises a functional material comprising one or more of a second polymer, a plasticizing compound, an ionic liquid, and an inorganic filler; The second polymer comprises one or more of polyvinyl alcohol, polyacrylonitrile, polyethylene, polyamide, polydimethylsiloxane, polystyrene, polycaprolactone, polylactic acid and polymethyl ethylene carbonate; The inorganic filler includes inorganic ceramic particles and inorganic solid electrolyte.

5. The battery separator according to claim 4, wherein The mass ratio of the polymer electrolyte to the functional material is 0.1 to 10.

6. The battery separator according to claim 1, wherein The base film has a thickness of 3 μm to 25 μm, and the coating has a thickness of 0.1 μm to 10 μm.

7. A method for preparing a battery separator according to claim 1, characterized in that: The preparation method comprises: mixing the polymer electrolyte raw materials to form a coating material; The coating material is coated on the surface of the base film to form the coating layer, and the coating method includes one or more of roll coating, spray coating, gravure coating and micro gravure coating.

8. The preparation method according to claim 7, wherein The coating material further includes a leveling agent and a thickener. Based on the coating material, the content of the leveling agent is 0.001 wt% to 0.1 wt%, the content of the thickener is 0.1 wt% to 5 wt%, and the viscosity of the coating material is 50 mPa·s to 3000 mPa·s.

9. A battery, characterized in that: The battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, wherein the separator comprises the battery separator according to any one of claims 1 to 6 or the battery separator prepared by the preparation method according to any one of claims 7 to 8.

10. An electrical device, characterized in that: The electric device comprises the battery as claimed in claim 9.

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